Temporal processing deficits of language-learning impaired children ameliorated by training

Time-warp-invariant neuronal processing

Fluctuations in the temporal durations of sensory signals constitute a major source of variability within natural stimulus ensembles. The neuronal mechanisms through which sensory systems can stabilize perception against such fluctuations are largely unknown. An intriguing instantiation of such robustness occurs in human speech perception, which relies critically on temporal acoustic cues that are embedded in signals with highly variable duration. Across different instances of natural speech, auditory cues can undergo temporal warping that ranges from 2-fold compression to 2-fold dilation without significant perceptual impairment. Here, we report that time-warp-invariant neuronal processing can be subserved by the shunting action of synaptic conductances that automatically rescales the effective integration time of postsynaptic neurons. We propose a novel spike-based learning rule for synaptic conductances that adjusts the degree of synaptic shunting to the temporal processing requirements of a given task. Applying this general biophysical mechanism to the example of speech processing, we propose a neuronal network model for time-warp-invariant word discrimination and demonstrate its excellent performance on a standard benchmark speech-recognition task. Our results demonstrate the important functional role of synaptic conductances in spike-based neuronal information processing and learning. The biophysics of temporal integration at neuronal membranes can endow sensory pathways with powerful time-warp-invariant computational capabilities.

Assessment of auditory processing in 6-year-old language-impaired children: Evaluacion del procesamiento auditivo en niños de 6 años con trastornos del lenguaje

The performance of a group of twenty 6-year-old children with specific language impairment (SLI) on several behavioural auditory tests was compared to that of a group of twenty age-matched control children. The auditory test battery used in this study consisted of the following tests: a speech-in-noise test, a filtered speech test, a binaural fusion test, a frequency pattern test, a duration pattern test, a temporal integration test, an auditory word discrimination test, an auditory synthesis test, an auditory closure test and a number recall test. Our results show that the SLI children obtained scores on almost all tests that were significantly lower than those of the control group. Many of the basic auditory processing measures in our test battery correlated significantly with receptive and language scores, suggesting a (causal) relationship between auditory processing and language proficiency. Results from discriminant function analyses do not warrant deleting one or more tests from the test battery yet (with the exception of the auditory synthesis test and the temporal integration test, for which we did not find significant group effects). At present, we are conducting experiments with older (SLI and control) children and adults to find whether the significant performance deficits of the SLI children are also found in older SLI children, and to determine the influence of maturational effects on these auditory tests.

Abnormal cortical processing of the syllable rate of speech in poor readers

Children with reading impairments have long been associated with impaired perception for rapidly presented acoustic stimuli and recently have shown deficits for slower features. It is not known whether impairments for low-frequency acoustic features negatively impact processing of speech in reading-impaired individuals. Here we provide neurophysiological evidence that poor readers have impaired representation of the speech envelope, the acoustical cue that provides syllable pattern information in speech. We measured cortical-evoked potentials in response to sentence stimuli and found that good readers indicated consistent right-hemisphere dominance in auditory cortex for all measures of speech envelope representation, including the precision, timing, and magnitude of cortical responses. Poor readers showed abnormal patterns of cerebral asymmetry for all measures of speech envelope representation. Moreover, cortical measures of speech envelope representation predicted up to 41% of the variability in standardized reading scores and 50% in measures of phonological processing across a wide range of abilities. Our findings strongly support a relationship between acoustic-level processing and higher-level language abilities, and are the first to link reading ability with cortical processing of low-frequency acoustic features in the speech signal. Our results also support the hypothesis that asymmetric routing between cerebral hemispheres represents an important mechanism for temporal encoding in the human auditory system, and the need for an expansion of the temporal processing hypothesis for reading disabilities to encompass impairments for a wider range of speech features than previously acknowledged.

Comorbidity of auditory processing, language, and reading disorders

PURPOSE

The authors assessed comorbidity of auditory processing disorder (APD), language impairment (LI), and reading disorder (RD) in school-age children.

METHOD

Children (N = 68) with suspected APD and nonverbal IQ standard scores of 80 or more were assessed using auditory, language, reading, attention, and memory measures. Auditory processing tests included the Frequency Pattern Test (FPT; F. E. Musiek, 1994; D. Noffsinger, R. H. Wilson, & F. E. Musiek, 1994); the Dichotic Digit Test Version 2 (DDT; F. E. Musiek, 1983); the Random Gap Detection Test (R. W. Keith, 2000); the 500-Hz tone Masking Level Difference (V. Aithal, A. Yonovitz, & S. Aithal, 2006); and a monaural low-redundancy speech test (compressed and reverberant words; A. Boothroyd & S. Nittrouer, 1988). The Clinical Evaluation of Language Fundamentals, Fourth Edition (E. Semel, E. Wiig, & W. Secord, 2003) was used to assess language abilities (including auditory memory). Reading accuracy and fluency and phonological awareness abilities were assessed using the Wheldall Assessment of Reading Passages (A. Madelaine & K. Wheldall, 2002) and the Queensland University Inventory of Literacy (B. Dodd, A. Holm, M. Orelemans, & M. McCormick, 1996). Attention was measured using the Integrated Visual and Auditory Continuous Performance Test (J. A. Sandford & A. Turner, 1995).

RESULTS

Of the children, 72% had APD on the basis of these test results. Most of these children (25%) had difficulty with the FPT bilaterally. A further 22% had difficulty with the FPT bilaterally and had right ear deficits for the DDT. About half of the children (47%) had problems in all 3 areas (APD, LI, and RD); these children had the poorest FPT scores. More had APD-RD, or APD-LI, than APD, RD, or LI alone. There were modest correlations between FPT scores and attention and memory, and between DDT scores and memory.

CONCLUSIONS

LI and RD commonly co-occur with APD. Attention and memory are linked to performance on some auditory processing tasks but only explain a small amount of the variance in scores. Comprehensive assessment across a range of areas is required to characterize the difficulties experienced by children with APD.

Perceptual learning and human expertise

We consider perceptual learning: experience-induced changes in the way perceivers extract information. Often neglected in scientific accounts of learning and in instruction, perceptual learning is a fundamental contributor to human expertise and is crucial in domains where humans show remarkable levels of attainment, such as language, chess, music, and mathematics. In Section 2, we give a brief history and discuss the relation of perceptual learning to other forms of learning. We consider in Section 3 several specific phenomena, illustrating the scope and characteristics of perceptual learning, including both discovery and fluency effects. We describe abstract perceptual learning, in which structural relationships are discovered and recognized in novel instances that do not share constituent elements or basic features. In Section 4, we consider primary concepts that have been used to explain and model perceptual learning, including receptive field change, selection, and relational recoding. In Section 5, we consider the scope of perceptual learning, contrasting recent research, focused on simple sensory discriminations, with earlier work that emphasized extraction of invariance from varied instances in more complex tasks. Contrary to some recent views, we argue that perceptual learning should not be confined to changes in early sensory analyzers. Phenomena at various levels, we suggest, can be unified by models that emphasize discovery and selection of relevant information. In a final section, we consider the potential role of perceptual learning in educational settings. Most instruction emphasizes facts and procedures that can be verbalized, whereas expertise depends heavily on implicit pattern recognition and selective extraction skills acquired through perceptual learning. We consider reasons why perceptual learning has not been systematically addressed in traditional instruction, and we describe recent successful efforts to create a technology of perceptual learning in areas such as aviation, mathematics, and medicine. Research in perceptual learning promises to advance scientific accounts of learning, and perceptual learning technology may offer similar promise in improving education.

Hebbian Reweighting on Stable Representations in Perceptual Learning

Perceptual learning is the improvement in perceptual task performance with practice or training. The observation of specificity in perceptual learning has been widely associated with plasticity in early visual cortex representations. Here, we review the evidence supporting the plastic reweighting of readout from stable sensory representations, originally proposed by Dosher & Lu (1998), as an alternative explanation of perceptual learning. A task-analysis that identifies circumstances in which specificity supports representation enhancement and those in which it implies reweighting provides a framework for evaluating the literature; reweighting is broadly consistent with the behavioral results and almost all of the physiological reports. We also consider the evidence that the primary mode of perceptual learning is through augmented Hebbian learning of the reweighted associations, which has implications for the role and importance of feedback. Feedback is not necessary for perceptual learning, but can improve it in some circumstances, and in some cases block feedback is also helpful - all effects that are generally compatible with an augmented Hebbian model (Petrov, Dosher, & Lu, 2005). The two principles of perceptual learning through reweighting evidence from stable sensory representations and of augmented Hebbian learning provide a theoretical structure for the consideration of issues such as task difficulty, task roving, and cuing in perceptual learning.

Brain basis of human social interaction: from concepts to brain imaging

Modern neuroimaging provides a common platform for neuroscience and related disciplines to explore the human brain, mind, and behavior. We base our review on the social shaping of the human mind and discuss various aspects of brain function related to social interaction. Despite private mental contents, people can share their understanding of the world using, beyond verbal communication, nonverbal cues such as gestures, facial expressions, and postures. The understanding of nonverbal messages is supported by the brain's mirroring systems that are shaped by individual experience. Within the organism-environment system, tight links exist between action and perception, both within an individual and between several individuals. Therefore, any comprehensive brain imaging study of the neuronal basis of social cognition requires appreciation of the situated and embodied nature of human cognition, motivating simultaneous monitoring of brain and bodily functions within a socially relevant environment. Because single-person studies alone cannot unravel the dynamic aspects of interpersonal interactions, it seems both necessary and beneficial to move towards "two-person neuroscience"; technological shortcomings and a limited conceptual framework have so far hampered such a leap. We conclude by discussing some major disorders of social interaction.

When "Simon says" doesn't work: alternatives to imitation for facilitating early speech development

PURPOSE

To provide clinicians with evidence-based strategies to facilitate early speech development in young children who are not readily imitating sounds. Relevant populations may include, but are not limited to, children with autism spectrum disorders, childhood apraxia of speech, and late-talking toddlers.

METHOD

Through multifaceted search procedures, we found experimental support for 6 treatment strategies that have been used to facilitate speech development in young children with developmental disabilities. Each strategy is highlighted within this article through a summary of the underlying rationale(s), empirical support, and specific examples of how it could be applied within intervention.

CONCLUSIONS

Given the relatively sparse experimental data focused on facilitating speech in children who do not readily imitate, theoretical support emerges as particularly key and underscores the need for clinicians to consider why they are doing what they are doing. In addition, this review emphasizes the need for the research community to bridge the gap between pressing clinical needs and the limited evidence base that is currently available.

The problem of not developing normally and pediatric neuropsychological rehabilitation: theMitchell Rosenthal Lecture

Children who suffer moderately severe-to-severe traumatic brain injury often fail to develop normal cognitive and affective functioning necessary for independent adult living. The cognitive and psychiatric consequences of pediatric traumatic brain injury are outlined and 6 barriers to providing neuropsychological rehabilitation for these children are identified. Suggestions are made to help reduce the impact of those barriers.

Application of neuroscience to technology in stroke rehabilitation

The past decade has seen remarkable advances in our understanding of mechanisms that drive functional neuroplastic change after brain injury and the mirror neuron system that appears essential for language learning and communicative interaction. This article describes five neuroscience-based interventions available for clinical practice, with a discussion of the potential value of mirror neurons in stroke rehabilitation. Case-study data on three adults with aphasia who received various combinations of neuroscience-derived technological interventions are provided to inform the clinician of the potential advantages of technology as an adjunct to, not a substitution for, conventional therapeutic intervention.

Backward and simultaneous masking in children with grammatical specific language impairment: no simple link between auditory and language abilities

PURPOSE

We investigated claims that specific language impairment (SLI) typically arises from nonspeech auditory deficits by measuring tone-in-noise thresholds in a relatively homogeneous SLI subgroup exhibiting a primary deficit restricted to grammar (Grammatical[G]-SLI).

METHOD

Fourteen children (mostly teenagers) with G-SLI were compared to age-, vocabulary-, and grammar-matched control children on their abilities to detect a brief tone in quiet and in the presence of a masking noise. The tone occurred either simultaneously with the noise or just preceding it (backward masking). Maskers with and without a spectral notch allowed estimates of frequency selectivity.

RESULTS

Group thresholds for the G-SLI children were never worse than those obtained for younger controls but were higher in both backward and simultaneous masking than in age-matched controls. However, more than half of the G-SLI group (8/14) were within age-appropriate limits for all thresholds. Frequency selectivity in the G-SLI group was normal. Within control and G-SLI groups, no threshold correlated with measures of vocabulary, grammar, or phonology. Nor did the language deficit in the G-SLI children vary with the presence or absence of auditory deficits.

CONCLUSION

The auditory processing deficits sometimes found in children with SLI appear unlikely to cause or maintain the language impairment.

Early acoustic discrimination experience ameliorates auditory processing deficits in male rats with cortical developmental disruption

Auditory temporal processing deficits have been suggested to play a causal role in language learning impairments, and evidence of cortical developmental anomalies (microgyria (MG), ectopia) has been reported for language-impaired populations. Rodent models have linked these features, by showing deficits in auditory temporal discrimination for rats with neuronal migration anomalies (MG, ectopia). Since evidence from human studies suggests that training with both speech and non-speech acoustic stimuli may improve language performance in developmentally language-disabled populations, we were interested in whether/how maturation and early experience might influence auditory processing deficits seen in male rats with induced focal cortical MG. Results showed that for both simple (Normal single tone), as well as increasingly complex auditory discrimination tasks (silent gap in white noise and FM sweep), prior experience significantly improved acoustic discrimination performance--in fact, beyond improvements seen with maturation only. Further, we replicated evidence that young adult rats with MG were significantly impaired at discriminating FM sweeps compared to shams. However, these MG effects were no longer seen when experienced subjects were retested in adulthood (even though deficits in short duration FM sweep detection were seen for adult MG rats with no early experience). Thus while some improvements in auditory processing were seen with normal maturation, the effects of early experience were even more profound, in fact resulting in amelioration of MG effects seen at earlier ages. These findings support the clinical view that early training intervention with appropriate acoustic stimuli could similarly ameliorate long-term processing impairments seen in some language-impaired children.

Statistical learning in children with specific language impairment

PURPOSE

In this study, the authors examined (a) whether children with specific language impairment (SLI) can implicitly compute the probabilities of adjacent sound sequences, (b) if this ability is related to degree of exposure, (c) if it is domain specific or domain general and, (d) if it is related to vocabulary.

METHOD

Children with SLI and normal language controls (ages 6;5-14;4 [years;months]) listened to 21 min of a language in which transitional probabilities within words were higher than those between words. In a second study, children with SLI and Age-Nonverbal IQ matched controls (8;0-10;11) listened to the same language for 42 min and to a second 42 min "tone" language containing the identical statistical structure as the "speech" language.

RESULTS

After 21 min, the SLI group's performance was at chance, whereas performance for the control group was significantly greater than chance and significantly correlated with receptive and expressive vocabulary knowledge. In the 42-minute speech condition, the SLI group's performance was significantly greater than chance and correlated with receptive vocabulary but was no different from chance in the analogous 42-minute tone condition. Performance for the control group was again significantly greater than chance in 42-minute speech and tone conditions.

CONCLUSIONS

These findings suggest that poor implicit learning may underlie aspects of the language impairments in SLI.

Specificity of binaural perceptual learning for amplitude modulated tones: a comparison of two training methods

The specificity of auditory perceptual learning has been taken as an indicator of the likely locus within the brain at which underlying neuronal changes occur. This study examined interaural level difference (ILD) discrimination learning with sinusoidally amplitude modulated (SAM) tones and whether training-induced threshold improvements generalize from one side of auditory space to the other and to an untrained carrier frequency. A novel, dual-staircase adaptive method was adopted that was designed to prevent participants from identifying the nature of the adaptive track. ILD thresholds obtained with this method were compared with a constant-stimulus technique using otherwise identical stimuli. Adaptive thresholds derived from psychometric functions were found to be biased compared to those obtained from reversals. Although adaptive and constant-stimulus procedures appeared to yield different temporal patterns of learning, no global differences were found between them in terms of training outcomes. These data show that ILD discrimination learning with SAM tones does generalize to an untrained carrier frequency but does not generalize across the midline. This implies that the neural substrate for binaural plasticity is found at a relatively high level of the auditory pathway where information is combined across frequency and where each side of auditory space is represented separately.

Use of auditory learning to manage listening problems in children

This paper reviews recent studies that have used adaptive auditory training to address communication problems experienced by some children in their everyday life. It considers the auditory contribution to developmental listening and language problems and the underlying principles of auditory learning that may drive further refinement of auditory learning applications. Following strong claims that language and listening skills in children could be improved by auditory learning, researchers have debated what aspect of training contributed to the improvement and even whether the claimed improvements reflect primarily a retest effect on the skill measures. Key to understanding this research have been more circumscribed studies of the transfer of learning and the use of multiple control groups to examine auditory and non-auditory contributions to the learning. Significant auditory learning can occur during relatively brief periods of training. As children mature, their ability to train improves, but the relation between the duration of training, amount of learning and benefit remains unclear. Individual differences in initial performance and amount of subsequent learning advocate tailoring training to individual learners. The mechanisms of learning remain obscure, especially in children, but it appears that the development of cognitive skills is of at least equal importance to the refinement of sensory processing. Promotion of retention and transfer of learning are major goals for further research.

Developmentally degraded cortical temporal processing restored by training

Enduring deficits in temporal processing can be induced in the auditory cortex by rearing infant rats in the presence of low frequency-modulated noises. We found that it was possible to restore normal temporal processing, overcoming deficits induced during the critical period, by intensively training developmentally impaired animals as juveniles or young adults. Re-normalized cortical temporal response characteristics were sustained long after training cessation.

Stimulus, task, and learning effects on measures of temporal resolution: implications for predictors of language outcome

PURPOSE

Some studies find that temporal processing ability predicts language outcome whereas other studies do not. Resolution of this debate is hindered by the variety of temporal measures used, nonsensory loading of the tasks, and differential amounts of practice across studies. The goal of this study was to examine the effects of stimulus properties, experimental task, and perceptual learning on listeners' gap detection performance.

METHOD

Gap detection thresholds were obtained from adults with normal hearing and language ability. The effects of marker frequency similarity and marker duration on thresholds were examined in yes-no, two-interval forced-choice (2IFC), and dual-pair comparison tasks (which vary in nonsensory loading) over 4 days of testing.

RESULTS

Thresholds were highest for gaps defined by markers with disparate frequencies (1000 and 4000 Hz; i.e., between-channel gap detection), and with longer (300 ms) trailing markers, obtained using yes-no and 2IFC tasks. However, these effects were attenuated with training or the initial use of the dual-pair comparison task.

CONCLUSIONS

These results suggest that gap detection thresholds reflect a variety of sensory and nonsensory factors. Understanding these underlying factors is critical to any evaluation of the relation between temporal processing and language outcome.

Exact solutions for rate and synchrony in recurrent networks of coincidence detectors

We provide analytical solutions for mean firing rates and cross-correlations of coincidence detector neurons in recurrent networks with excitatory or inhibitory connectivity, with rate-modulated steady-state spiking inputs. We use discrete-time finite-state Markov chains to represent network state transition probabilities, which are subsequently used to derive exact analytical solutions for mean firing rates and cross-correlations. As illustrated in several examples, the method can be used for modeling cortical microcircuits and clarifying single-neuron and population coding mechanisms. We also demonstrate that increasing firing rates do not necessarily translate into increasing cross-correlations, though our results do support the contention that firing rates and cross-correlations are likely to be coupled. Our analytical solutions underscore the complexity of the relationship between firing rates and cross-correlations.

Individual differences in the perception of temporal order: the effect of age and cognition

Temporal-order judgements in the time range of some milliseconds were assessed by using two auditory tasks in 86 participants, aged from 20 to 69 years. Two stimulus presentation modes, binaural versus monaural, were compared. Elderly participants performed worse than the younger participants; however, different patterns of age-related declines were observed, depending on the presentation mode. In the monaural mode considerable deterioration was observed beyond 60 years of age, whereas in the binaural mode declines were found much earlier, from 40 years of age. Performance of the monaural task correlated with cognitive competences and provided important insight into neuronal timing mechanisms. In contrast, the binaural mode reflected a bias towards an integrated perception of sequential stimuli and was less related to cognitive resources. These findings provide evidence that age-related declines in human sequencing abilities involve, besides temporal mechanisms, also a mode-specific processing, presumably associated with different neuronal mechanisms.

Combined auditory and articulatory training improves phonological deficit in children with dyslexia

A group of 19 children with dyslexia aged 7 years 2 months to 10 years 9 months were selected from a clinical sample and tested using a large neuropsychological battery in order to specify the severity and subtype of dyslexia as well as the presence of comorbid conditions. Thereafter, they received a standardised training of 6 weeks of daily auditory exercises aimed at reinforcing explicit and implicit phonological awareness. Ten participants also received specific training of the sensory-motor aspects of articulatory production of individual phonemes during the first 3 weeks of auditory training, whereas the remaining received the same specific training during the last 3 weeks of auditory training. Repetition, phonological awareness, reading and spelling were assessed before the first session, between the two sessions and after the second session. Results confirm the overall efficiency of intensive phonological training, even with exclusively auditory material. The main outcome of this study is a significant improvement of phonology and non-word reading specifically during the periods where the two methods were associated, suggesting a significant contribution of articulatory training to the observed improvement. Finally performance to a motor tapping task proved to be one of the best predictors of training efficiency while comorbid co-ordination or attention deficit did not interfere. Results are interpreted with reference to current theories about mechanisms underlying dyslexia.

Using time-to-contact information to assess potential collision modulates both visual and temporal prediction networks

Accurate estimates of the time-to-contact (TTC) of approaching objects are crucial for survival. We used an ecologically valid driving simulation to compare and contrast the neural substrates of egocentric (head-on approach) and allocentric (lateral approach) TTC tasks in a fully factorial, event-related fMRI design. Compared to colour control tasks, both egocentric and allocentric TTC tasks activated left ventral premotor cortex/frontal operculum and inferior parietal cortex, the same areas that have previously been implicated in temporal attentional orienting. Despite differences in visual and cognitive demands, both TTC and temporal orienting paradigms encourage the use of temporally predictive information to guide behaviour, suggesting these areas may form a core network for temporal prediction. We also demonstrated that the temporal derivative of the perceptual index tau (tau-dot) held predictive value for making collision judgements and varied inversely with activity in primary visual cortex (V1). Specifically, V1 activity increased with the increasing likelihood of reporting a collision, suggesting top-down attentional modulation of early visual processing areas as a function of subjective collision. Finally, egocentric viewpoints provoked a response bias for reporting collisions, rather than no-collisions, reflecting increased caution for head-on approaches. Associated increases in SMA activity suggest motor preparation mechanisms were engaged, despite the perceptual nature of the task.

Effects of a computer-assisted language intervention in a rural Nevada center

A computer-assisted language intervention, Fast ForWord-Language (FFW-L), was tested at a rural Nevada center in a group of children (Grades 2-12) referred by parents and teachers to assess enhancement of language skills. Given conflicting results from previous studies, language scores were measured using Clinical Evaluation of Language Fundamentals, Third Edition (CELF-3) before and after the FFW-L intervention. 58 children's CELF-3 postintervention scores were adjusted for age-specific expected changes and compared with pretest scores. Adjusted scores increased in both receptive and expressive domains of the CELF-3. Children with prior diagnoses of language and/or learning impairment did not differ from other referrals on adjusted CELF-3 adjusted gain scores after treatment. Thus the Fast ForWord-Language intervention may benefit a much broader group of children referred by parents and teachers for language or reading problems.

Maximizing cochlear implant patients' performance with advanced speech training procedures

Advances in implant technology and speech processing have provided great benefit to many cochlear implant patients. However, some patients receive little benefit from the latest technology, even after many years' experience with the device. Moreover, even the best cochlear implant performers have great difficulty understanding speech in background noise, and music perception and appreciation remain major challenges. Recent studies have shown that targeted auditory training can significantly improve cochlear implant patients' speech recognition performance. Such benefits are not only observed in poorly performing patients, but also in good performers under difficult listening conditions (e.g., speech noise, telephone speech, music, etc.). Targeted auditory training has also been shown to enhance performance gains provided by new implant devices and/or speech processing strategies. These studies suggest that cochlear implantation alone may not fully meet the needs of many patients, and that additional auditory rehabilitation may be needed to maximize the benefits of the implant device. Continuing research will aid in the development of efficient and effective training protocols and materials, thereby minimizing the costs (in terms of time, effort and resources) associated with auditory rehabilitation while maximizing the benefits of cochlear implantation for all recipients.

A randomized, controlled study of computer-based intervention in middle school struggling readers

The current study was conducted to test the premise that computer-based intervention that targets auditory temporal processing combined with language exercises (Fast ForWord) is effective in remediating children with disorders of language and reading. Sixty-five middle school struggling readers were randomly assigned to one of five groups and over a 12-week-period received one of the following interventions: (1) two phases of intervention with Fast ForWord (FFW, experimental group), (2) two phases of intervention with SuccessMaker (SM, active control group), (3) FFW followed by SM, (4) SM followed by FFW, or (5) no intervention beyond the regular class curriculum (developmental control group). Changes in reading, phonemic awareness, spelling and language skills were assessed via a repeated measures MANOVA. Results indicated significant within-subjects effects (i.e., change for all participants over time), but no between-subject group differences, failing to show that Fast ForWord resulted in any gains over and above those seen in the other groups.

Can auditory and visual speech perception be trained within a group setting?

PURPOSE

This study attempted to determine whether auditory-only and auditory-visual speech perception could be trained in a group format.

METHOD

A randomized controlled trial with at least 16 participants per group was completed. A training-only group completed at least 5 hr of group speech perception training; a training plus psychosocial group completed at least 5 hr of group speech perception training and psychosocial exercises; and a control group did not receive training. Evaluations were conducted before and after training and included analytic and synthetic measures of speech perception, hearing loss-related and generic quality of life scales, and a class evaluation form.

RESULTS

No significant group changes were measured on any of the analytic auditory-only or auditory-visual measures of speech perception, yet the majority of training participants (regardless of training group) reported improvement in auditory and auditory-visual speech perception. The training participants demonstrated a significant reduction on the emotional subscale of the hearing loss-related quality of life scale, while the control participants did not demonstrate a change on this subscale.

CONCLUSIONS

Benefits of group audiologic rehabilitation classes may not result from an actual improvement in auditory or visual speech perception abilities, but participants still perceive training in these areas as useful.

Frequency discrimination learning in children

Psychoacoustic thresholds of pure tone frequency discrimination (FD) in children are elevated relative to those of adults. It has been shown that it is possible to improve FD thresholds in adults, following a single (subhour) training session. To determine whether FD thresholds in children may be improved by training and, consequently, reduced to adult levels, 100 normally hearing 6- to 11-year-old children and adults received approximately 1 h of training on a FD task at 1 kHz. At the start of training, a quarter of all child participants had FD thresholds that resembled those of naive adults (adult-like subgroup). Another quarter achieved thresholds that were adult-like at some point during training (trainable subgroup). For the remainder (nonadult-like subgroup), thresholds did not reach those of naive adult listeners at any point in the training session. Subgroup membership was linked to the influence of three factors-age, nonverbal IQ, and attention. However, across subgroups, learning was found not to generalize to either a different standard frequency (4 kHz) or a variable (roving) presentation paradigm. The results indicate that it is possible for some children to achieve FD thresholds comparable to those of naive adults, either natively or after limited training.

Fully optimized discrimination of physiological responses to auditory stimuli

The use of multivariate measurements to characterize brain activity (electrical, magnetic, optical) is widespread. The most common approaches to reduce the complexity of such observations include principal and independent component analyses (PCA and ICA), which are not well suited for discrimination tasks. We addressed two questions: first, how do the neurophysiological responses to elongated phonemes relate to tone and phoneme responses in normal children, and, second, how discriminable are these responses. We employed fully optimized linear discrimination analysis to maximally separate the multi-electrode responses to tones and phonemes, and classified the response to elongated phonemes. We find that discrimination between tones and phonemes is dependent upon responses from associative regions of the brain apparently distinct from the primary sensory cortices typically emphasized by PCA or ICA, and that the neuronal correlates corresponding to elongated phonemes are highly variable in normal children (about half respond with neural correlates of tones and half as phonemes). Our approach is made feasible by the increase in computational power of ordinary personal computers and has significant advantages for a wide range of neuronal imaging modalities.

The easy-to-hard effect in human (Homo sapiens) and rat (Rattus norvegicus) auditory identification

The authors examined whether progressively training humans and rats to perform a difficult auditory identification task led to larger improvements than extensive training with highly similar sounds (the easy-to-hard effect). Practice improved humans' ability to distinguish sounds regardless of the training regimen. However, progressively trained subjects were more accurate and showed more generalization, despite significantly less training with the stimuli that were the most difficult to distinguish. Rats showed less capacity to improve with practice but still benefited from progressive training. These findings indicate that transitioning from an easier to a more difficult task during training can facilitate, and in some cases may be essential for, auditory perceptual learning. The results are not predicted by an explanation that assumes interaction of generalized excitation and inhibition but are consistent with a hierarchical account of perceptual learning in which the representational precision required to distinguish stimuli determines the mechanisms engaged during learning.

Global versus local processing of frequency-modulated tones in gerbils: an animal model of lateralized auditory cortex functions

Hemispheric asymmetries of speech and music processing might arise from more basic specializations of left and right auditory cortex (AC). It is not clear, however, whether such asymmetries are unique to humans, i.e., consequences of speech and music, or whether comparable lateralized AC functions exist in nonhuman animals, as evolutionary precursors. Here, we investigated the cortical lateralization of perception of linearly frequency-modulated (FM) tones in gerbils, a rodent species with human-like low-frequency hearing. Using a footshock-reinforced shuttle-box avoidance go/no-go procedure in a total of 178 gerbils, we found that (i) the discrimination of direction of continuous FM (rising versus falling sweeps, 250-ms duration) was impaired by right but not left AC lesions; (ii) the discrimination of direction of segmented FM (50-ms segments, 50-ms silent gaps, total duration 250 ms) was impaired by bilateral but not unilateral AC lesions; (iii) the discrimination of gap durations (10-30 ms) in segmented FM was impaired by left but not right AC lesions. AC lesions before and after training resulted in similar effects. Together, these experiments suggest that right and left AC, even in rodents, use different strategies in analyzing FM stimuli. Thus, the right AC, by using global cues, determines the direction of continuous and segmented FM but cannot discriminate gap durations. The left AC, by using local cues, discriminates gap durations and determines FM direction only when additional segmental information is available.

Frequency discrimination in children: perception, learning and attention

It is generally believed that both sensory immaturity and inattention contribute to the poor listening of some children. However, the relative contribution of each factor, within and between individuals, and the nature of the inattention are poorly understood. In three experiments we examined the threshold and response variability of 6-11 y.o. children on pure tone frequency discrimination (FD) tasks. We first confirmed that younger children had both higher thresholds and greater within- and between-listener variability than older children and adults. Higher thresholds were mostly attributed to high response variability due to poor sustained attention. We next compared performance on the auditory FD task with that on visual spatial FD. No correlation was found between the thresholds or variability of individuals on the two tasks, suggesting involvement of modality-specific attention. Finally, we found lower thresholds for 8-9 y.o. children performing auditory FD training in a classroom than in the laboratory, possibly due to training session length or to a more familiar, motivating and focussed training environment. The adult-like performance of many younger children at times during their testing or training, together with the high response variability of immature performers, suggested that most elevated FD thresholds in children are due to inattention.

Language intervention practices for school-age children with spoken language disorders: a systematic review

PURPOSE

This systematic review focuses on peer-reviewed articles published since 1985 that assess the outcomes of language intervention practices for school-age students with spoken language disorders.

METHOD

We conducted computer searches of electronic databases and hand searches of other sources for studies that used experimental designs that were considered to be reliable and valid: randomized clinical trials, nonrandomized comparison studies, and multiple-baseline single-subject design studies.

RESULTS

The review yielded 21 studies concerning the efficacy or effectiveness of language intervention practices with school-age children since 1985. Eleven of the studies limited participants to children in kindergarten and first grade, and no studies were located that focused on students in middle grades or high school. The relatively high quality of the studies that met our criteria, and the moderate-to-high effect sizes we calculated for the majority of studies, suggests that clinicians can have some confidence in the specific language intervention practices examined.

CONCLUSION

The fact that only 21 studies met our criteria means that there is relatively little evidence supporting the language intervention practices that are currently being used with school-age children with language disorders. We outline significant gaps in the evidence and discuss the implications for clinical practice in schools.

Phonetic learning as a pathway to language: new data and native language magnet theory expanded (NLM-e)

Infants' speech perception skills show a dual change towards the end of the first year of life. Not only does non-native speech perception decline, as often shown, but native language speech perception skills show improvement, reflecting a facilitative effect of experience with native language. The mechanism underlying change at this point in development, and the relationship between the change in native and non-native speech perception, is of theoretical interest. As shown in new data presented here, at the cusp of this developmental change, infants' native and non-native phonetic perception skills predict later language ability, but in opposite directions. Better native language skill at 7.5 months of age predicts faster language advancement, whereas better non-native language skill predicts slower advancement. We suggest that native language phonetic performance is indicative of neural commitment to the native language, while non-native phonetic performance reveals uncommitted neural circuitry. This paper has three goals: (i) to review existing models of phonetic perception development, (ii) to present new event-related potential data showing that native and non-native phonetic perception at 7.5 months of age predicts language growth over the next 2 years, and (iii) to describe a revised version of our previous model, the native language magnet model, expanded (NLM-e). NLM-e incorporates five new principles. Specific testable predictions for future research programmes are described.

Enduring effects of early structured noise exposure on temporal modulation in the primary auditory cortex

Studies have shown that acoustic experiences significantly contribute to the functional shaping of the structural organization and signal processing capacities of the mammalian auditory system during postnatal development. Here, we show how an early epoch of exposure to structured noise influences temporal processing in the rat primary auditory cortex documented immediately after exposure and again in adulthood. Pups were continuously exposed to broadband-pulsed noise across the critical period for auditory system development. Immediately after cessation of exposure at postnatal day approximately 35 (P35) or approximately 55 days later (i.e., P90) in other rats, the temporal modulation-transfer functions of cortical neurons were documented. We found that pulsed noise exposure at a low modulation rate significantly decreased cortical responses to repetitive stimuli presented across a range of higher modulation rates. The highest temporal rate at which temporal modulation-transfer function was at half of its maximum was reduced when compared with naïve rats. Low-rate pulsed noise exposure also decreased cortical response synchronization at higher stimulus rates, as shown by vector strength and Rayleigh statistic measures. These postexposure changes endured into adulthood. These findings bear significant implications for the role of early sound experiences as contributors to the ontogeny of human auditory and language-related abilities and impairments.

Auditory processing disorders: an update for speech-language pathologists

PURPOSE

Unanswered questions regarding the nature of auditory processing disorders (APDs), how best to identify at-risk students, how best to diagnose and differentiate APDs from other disorders, and concerns about the lack of valid treatments have resulted in ongoing confusion and skepticism about the diagnostic validity of this label. This poses challenges for speech-language pathologists (SLPs) who are working with school-age children and whose scope of practice includes APD screening and intervention. The purpose of this article is to address some of the questions commonly asked by SLPs regarding APDs in school-age children. This article is also intended to serve as a resource for SLPs to be used in deciding what role they will or will not play with respect to APDs in school-age children.

METHOD

The methodology used in this article included a computerized database review of the latest published information on APD, with an emphasis on the work of established researchers and expert panels, including articles from the American Speech-Language-Hearing Association and the American Academy of Audiology.

CONCLUSIONS

The article concludes with the authors' recommendations for continued research and their views on the appropriate role of the SLP in performing careful screening, making referrals, and supporting intervention.

The efficacy of Fast ForWord Language intervention in school-age children with language impairment: a randomized controlled trial

PURPOSE

A randomized controlled trial was conducted to compare the language and auditory processing outcomes of children assigned to receive the Fast ForWord Language intervention (FFW-L) with the outcomes of children assigned to nonspecific or specific language intervention comparison treatments that did not contain modified speech.

METHOD

Two hundred sixteen children between the ages of 6 and 9 years with language impairments were randomly assigned to 1 of 4 conditions: (a) Fast ForWord Language (FFW-L), (b) academic enrichment (AE), (c) computer-assisted language intervention (CALI), or (d) individualized language intervention (ILI) provided by a speech-language pathologist. All children received 1 hr and 40 min of treatment, 5 days per week, for 6 weeks. Language and auditory processing measures were administered to the children by blinded examiners before treatment, immediately after treatment, 3 months after treatment, and 6 months after treatment.

RESULTS

The children in all 4 conditions improved significantly on a global language test and a test of backward masking. Children with poor backward masking scores who were randomized to the FFW-L condition did not present greater improvement on the language measures than children with poor backward masking scores who were randomized to the other 3 conditions. Effect sizes, analyses of standard error of measurement, and normalization percentages supported the clinical significance of the improvements on the Comprehensive Assessment of Spoken Language (E. Carrow-Woolfolk, 1999). There was a treatment effect for the Blending Words subtest of the Comprehensive Test of Phonological Processing (R. K. Wagner, J. K. Torgesen, & C. A. Rashotte, 1999). Participants in the FFW-L and CALI conditions earned higher phonological awareness scores than children in the ILI and AE conditions at the 6-month follow-up testing.

CONCLUSION

Fast ForWord Language, the intervention that provided modified speech to address a hypothesized underlying auditory processing deficit, was not more effective at improving general language skills or temporal processing skills than a nonspecific comparison treatment (AE) or specific language intervention comparison treatments (CALI and ILI) that did not contain modified speech stimuli. These findings call into question the temporal processing hypothesis of language impairment and the hypothesized benefits of using acoustically modified speech to improve language skills. The finding that children in the 3 treatment conditions and the active comparison condition made clinically relevant gains on measures of language and temporal auditory processing informs our understanding of the variety of intervention activities that can facilitate development.

Auditory temporal resolution in children assessed by magnetoencephalography

By means of magnetoencephalography we investigated the auditory-evoked fields (AEFs) elicited by broadband noise bursts in a gap-detection paradigm in children. AEFs of 16 healthy children (mean age 8.7 years) were recorded while they passively listened to 100-ms white-noise bursts with temporal gaps of 3, 6, 10 and 30 ms inserted after 5 or 50 ms. The peak of the earliest and largest positivity occurred at 97 ms and was evaluated by spatiotemporal source analysis. Psychophysical gap-detection thresholds were obtained for the same children. We found that the neuromagnetic gap responses corresponded to the psychoacoustic thresholds. AEFs thus provide an objective tool to assess auditory temporal resolution in children. Children's neuromagnetic response patterns differed significantly from the adult responses under the same experimental conditions.

Wide and Diffuse Perceptual Modes Characterize Dyslexics in Vision and Audition

We examined the performance of dyslexic and typically reading children on two analogous recognition tasks: one visual and the other auditory. Both tasks required recognition of centrally and peripherally presented stimuli. Dyslexics recognized letters visually farther in the periphery and more diffuse near the center than typical readers did. Both groups performed comparably in recognizing centrally spoken stimuli presented without peripheral interference, but in the presence of a surrounding speech mask (the ‘cocktail-party effect’) dyslexics recognized the central stimuli significantly less well than typical readers. However, dyslexics had a higher ratio of the number of words recognized from the surrounding speech mask, relative to the ones from the center, than typical readers did. We suggest that the evidence of wide visual and auditory perceptual modes in dyslexics indicates wider multi-dimensional neural tuning of sensory processing interacting with wider spatial attention.

A comparison between computer and tabletop delivery of phonology therapy

This paper reports on the development and evaluation of a software program aimed at assisting children with phonological impairment. An experimental approach was used whereby children's speech output was assessed pre- and post-therapy. Children were randomly assigned to a computer, a tabletop or a no therapy group. Those children receiving the computer therapy were exposed to an experimental software program that mirrored the tabletop activities using interactive computer games. The results showed no significant difference between any of the three groups with regard to change in speech output. These results may relate to the amount and frequency of therapy given and also to the heterogeneous nature of children included in the study. There was considerable variation in individual performance across all three groups and the data were therefore analysed to look for patterns that might predict performance. Stimulability and gender were identified as possible predictors. Female children and those who were able to produce a greater number of consonant speech sounds in isolation were more likely to make progress in their speech output. Future research might use a similar methodology to compare the therapy conditions but with a more homogenous group in terms of stimulability and using a greater intensity of intervention.

Electrical brain imaging evidences left auditory cortex involvement in speech and non-speech discrimination based on temporal features

BACKGROUND

Speech perception is based on a variety of spectral and temporal acoustic features available in the acoustic signal. Voice-onset time (VOT) is considered an important cue that is cardinal for phonetic perception.

METHODS

In the present study, we recorded and compared scalp auditory evoked potentials (AEP) in response to consonant-vowel-syllables (CV) with varying voice-onset-times (VOT) and non-speech analogues with varying noise-onset-time (NOT). In particular, we aimed to investigate the spatio-temporal pattern of acoustic feature processing underlying elemental speech perception and relate this temporal processing mechanism to specific activations of the auditory cortex.

RESULTS

Results show that the characteristic AEP waveform in response to consonant-vowel-syllables is on a par with those of non-speech sounds with analogue temporal characteristics. The amplitude of the N1a and N1b component of the auditory evoked potentials significantly correlated with the duration of the VOT in CV and likewise, with the duration of the NOT in non-speech sounds.Furthermore, current density maps indicate overlapping supratemporal networks involved in the perception of both speech and non-speech sounds with a bilateral activation pattern during the N1a time window and leftward asymmetry during the N1b time window. Elaborate regional statistical analysis of the activation over the middle and posterior portion of the supratemporal plane (STP) revealed strong left lateralized responses over the middle STP for both the N1a and N1b component, and a functional leftward asymmetry over the posterior STP for the N1b component.

CONCLUSION

The present data demonstrate overlapping spatio-temporal brain responses during the perception of temporal acoustic cues in both speech and non-speech sounds. Source estimation evidences a preponderant role of the left middle and posterior auditory cortex in speech and non-speech discrimination based on temporal features. Therefore, in congruency with recent fMRI studies, we suggest that similar mechanisms underlie the perception of linguistically different but acoustically equivalent auditory events on the level of basic auditory analysis.

Avaliação da habilidade de resolução temporal, com uso do tom puro, em crianças com e sem desvio fonológico

OBJETIVO: verificar o desempenho da resolução temporal em crianças portadoras de desvio fonológico. MÉTODOS: a área de estudo foi uma clínica escola de Fonoaudiologia de uma universidade particular do Recife e teve como participantes 36 crianças, de 6 a 9 anos, subdivididas em um grupo experimental (com desvio fonológico) e um grupo controle. Para a coleta de dados foi utilizado o Teste de detecção de intervalos aleatórios proposto por Keith e a análise quantitativa dos dados foi realizada com o SPSS 13 para a aplicação de técnicas de estatística descritiva. RESULTADOS: 94,5% das crianças com desvio fonológico apresentaram resultados alterados para o RGDT, os resultados mostram limiares de detecção de intervalos aleatórios maiores no grupo com desvio fonológico (25,00 a 28,33 ms); tendo sido significativa a diferença entre grupos para cada uma das freqüências testadas; não houve influência das variáveis: freqüência, sexo, idade e série escolar; o tratamento fonoaudiológico não foi um fator determinante; as queixas de aprendizagem mais referidas foram: dificuldade de leitura e dificuldade de compreensão de textos. CONCLUSÃO: crianças com desvio fonológico podem apresentar alteração de processamento temporal e necessitam de mais tempo para detecção de intervalos de tempo entre estímulos auditivos que as crianças sem desvio fonológico. De maneira geral, em ambos os grupos, não houve influência das variáveis: freqüência, sexo, idade, série escolar ou ocorrência de tratamento fonoaudiológico. As queixas de aprendizado podem estar presentes nas crianças com desvio fonológico e alteração de processamento temporal.

Decoding of temporal intervals from cortical ensemble activity

Neurophysiological, neuroimaging, and lesion studies point to a highly distributed processing of temporal information by cortico-basal ganglia-thalamic networks. However, there are virtually no experimental data on the encoding of behavioral time by simultaneously recorded cortical ensembles. We predicted temporal intervals from the activity of hundreds of neurons recorded in motor and premotor cortex as rhesus monkeys performed self-timed hand movements. During the delay periods, when animals had to estimate temporal intervals and prepare hand movements, neuronal ensemble activity encoded both the time that elapsed from the previous hand movement and the time until the onset of the next. The neurons that were most informative of these temporal intervals increased or decreased their rates throughout the delay until reaching a threshold value, at which point a movement was initiated. Variability in the self-timed delays was explainable by the variability of neuronal rates, but not of the threshold. In addition to predicting temporal intervals, the same neuronal ensemble activity was informative for generating predictions that dissociated the delay periods of the task from the movement periods. Left hemispheric areas were the best source of predictions in one bilaterally implanted monkey overtrained to perform the task with the right hand. However, after that monkey learned to perform the task with the left hand, its left hemisphere continued and the right hemisphere started contributing to the prediction. We suggest that decoding of temporal intervals from bilaterally recorded cortical ensembles could improve the performance of neural prostheses for restoration of motor function.

Auditory priming of frequency and temporal information: effects of lateralised presentation

Asymmetric distribution of function between the cerebral hemispheres has been widely investigated in the auditory modality. The current approach borrows heavily from visual local-global research in an attempt to determine whether, as in vision, local-global auditory processing is lateralised. In vision, lateralised local-global processing likely relies on spatial frequency information. Drawing analogies between visual spatial frequency and auditory dimensions, two sets of auditory stimuli were developed. In the high-low stimulus set we manipulate frequency information, and in the fast-slow stimulus set we manipulate temporal information. The fast-slow stimuli additionally mimic visual hierarchical stimulus structure, in which the arrangement of local patterns determines the global pattern. Unlike previous auditory stimuli, the current stimulus sets contain the experimental flexibility of visual local-global hierarchical stimuli allowing independent manipulation of structural levels. Previous findings of frequency and temporal range priming were replicated. Additionally, by presenting stimuli monaurally, we found that priming of frequency ranges (but not temporal ranges) was found to vary by ear, supporting the contention that the hemispheres asymmetrically retain traces of prior frequency processing. These results contribute to the extensive literature revealing cerebral asymmetries for the processing of frequency information, and extend those results to the realm of priming.

Treatment effects of Fast ForWord demonstrated by magnetoencephalography (MEG) in a child with developmental dyslexia

Treatment effects of Fast ForWord, hypothesized to ameliorate temporal processing deficits, were demonstrated by magnetoencephalography in a child with dyslexia using four paradigms: Word/Non-word Reading (NW), Grapheme-to-Phoneme Matching (GP), Verbal, and Spatial Working Memory (VWM, SWM). Shifts in brain activation from right inferior frontal and temporal to left frontal, bilateral supramarginal, and transverse temporal regions occurred during GP. During NW, shifts progressed from (1) right or bilateral anterior and superior to (2) left, inferior frontal, to (3) left, superior posterior temporoparietal, to (4) left, inferior, posterior temporooccipital regions. Reading and written language improvements were noted in passage comprehension and spelling.

Learning to discriminate interaural time differences at low and high frequencies

This study investigated learning, in normal-hearing adults, associated with training (i.e. repeated practice) on the discrimination of ongoing interaural time difference (ITD). Specifically, the study addressed an apparent disparity in the conclusions of previous studies, which reported training-induced learning at high frequencies but not at low frequencies. Twenty normal-hearing adults were trained with either low- or high-frequency stimuli, associated with comparable asymptotic thresholds, or served as untrained controls. Overall, trained listeners learnt more than controls and over multiple sessions. The magnitudes and time-courses of learning with the low- and high-frequency stimuli were similar. While this is inconsistent with the conclusion of a previous study with low-frequency ITD, this previous conclusion may not be justified by the results reported. Generalization of learning across frequency was found, although more detailed investigations of stimulus-specific learning are warranted. Overall, the results are consistent with the notion that ongoing ITD processing is functionally uniform across frequency. These results may have implications for clinical populations, such as users of bilateral cochlear implants.